Vibrating separating apparatus having adjustable material advancing rate

ABSTRACT

Vibratory separating apparatus wherein the screen basket assembly is mounted on the base by mounting means including resilient elements which are resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of the assembly relative to the base. The orbital vibrating movement is created by vibration generating means including rotatably driven eccentric means; and mounting means are provided for mounting the vibration generating means at a plurality of alternative positions adjusted longitudinally of the screen whereby the rate of advance of material longitudinally along the screen feed face by orbital vibrating movement of the screen is adjustable independently of the intensity and the amplitude of the vibrations by varying the location at which the vibration generating means is mounted by the mounting means.

[ 1 Oct. 2, 1973 FOREIGN PATENTS OR APPLICATIONS I I,357,330 2/l964 209/4l2 Primary ExaminerFrank W. Lutter Assistant Examiner-William Cuchlinski, Jr. AtlorneyCarl R. Horten et al.

[57] ABSTRACT Vibratory separating apparatus wherein the screen basket assembly is mounted on the base by mounting means including resilient elements which are resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of the assembly relative to the base. The orbital vibrating movement is created by vibration generating means including rotatably driven eccentric means; and mounting means are provided for mounting the vibration generating means at a plurality of alternative positions adjusted longitudinally of the screen whereby the rate of advance of material longitudinally along the VIBRATING SEPARATING APPARATUS HAVING ADJUSTABLE MATERIAL ADVANCING RATE Inventor: Sidney E. Stirk, Nashua, NH.

Assignee: Improved Machinery Inc., Nashua,

Filed: Mar. 19, 1972 Appl. No.: 233,494

Related US, Application Data Continuation of Ser. No. 865,827, Oct. 13, I969.

U.S. 209/326, 209/366.5, 209/405 Int. B07b 1/34 Field of Search................,... 204/326, 269, 415

References Cited UNITED STATES PATENTS United States Patent 1 Stirk screen feed face by orbital vibrating movement of the screen is adjustable independently of the intensity and the amplitude of the vibrations by varying the location at which the vibration generating means is mounted by 9 Claims, 10 Drawing Figures t 69 6 2 22 2X BBwMBQMM 99 99 9 003 /0050 22992292 00 .0.

Holman et al.

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s e 5 e FIG. 5B F/G.5C

(K INVENTOR e SIDNEY E. srmx ATTORNEY PATENTEW 3.762.547

SHEET 2 [1F 2 INVENTOR SIDNEY E. ST/RK ATTORNFY VIBRATING SEPARATING APPARATUS HAVING ADJUSTABLE MATERIAL ADVANCING RATE BACKGROUND OF THE INVENTION This application is a continuation of application Ser. No. 865,827, filed Oct. 13, 1969 now abandoned.

The present invention relates to vibratory separating apparatus and more particularly to vibratory separating apparatus of the type wherein the vibrating movement is caused by rotatably driven eccentric weights.

Conventionally, vibratory separating apparatus of this type is frequently employed in the pulp making process as drainers, knotters, bull screens, thickeners and scalpers. In a conventional vibratory separator, however, the rate of material advance longitudinally along the feed or screening face of the screen normally has been adjustable only by either angularly or radially adjusting the eccentric weights, varying the axial spacing between the weights or changing the magnitude of the weights. These methods of adjusting the rate of material movement are believed to be undesirable in that they inherently simultaneously result in variation in the intensity or amplitude of the vibrations. Increased vibration intensity causes greatly increased wear and abuse to the apparatus; and a relatively violent vibrating intensity fractionates the rejected material into smaller particles which pass through the screen to thereby contaminate the accepts.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new and improved vibratory separating apparatus which is particularly constructed and arranged to permit adjustment of the rate of material movement longitudinally along the'screen feed face without variation in the intensity or the amplitude of the vibrations.

Another object of the invention is to provide a new and improved vibratory separating apparatus of the type set forth which is particularly constructed and arranged to permit such adjustment in a relatively simple and efficient manner. I

These objects, and those other objects and advantages of the invention which will be apparent from the following description taken in connection with the accompanying drawings, are attained by the provision of a vibratory separating apparatus in general comprising a base, an assembly including supporting means and a screen connected to the supporting means, the screen having openings for separating material passed longitudinally along one face of the screen into a portion accepted by the openings and a portion rejected by the openings, mounting meansmounting the assembly on the base for orbital vibrating movement relative to the base, this assembly mounting means including resilient means at one end connected to the base andat the other end supporting the assembly, the resilient means being resilient laterally and longitudinally to be longitudinally extensible and compressible to permit'orbital vibrating movement of the assembly relative to the base, vibration generating means including eccentric means adapted to be rotatably driven for causing orbital vibrating movement of the assembly, and mounting means for mounting the vibration generating means on the supporting means at a plurality of alternative positions adjusted longitudinally of the screen whereby the rate of advance of material longitudinally along the one face of the screen by the orbital vibrating movement of the screen is adjustable independently of the intensity and the amplitude of the vibrations by varying the location at which the vibration generating means is mounted on the supporting means by the mounting means.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings:

FIG. 1 is a view in perspective of a vibratory separating apparatus constructed in accordance with one embodiment of the invention;

FIG. 2 is an enlarged, fragmentary top or plan view showing the mounting of the vibration generating means of the apparatus illustrated in FIG. 1;

FIG. 3 is an exploded view of such vibration generating means;

FIGS. 4A, 4B, and 4C are diagramatic views illustrating the orbits of the screen at the screen discharge end, center of gravity of the screen basket assembly, and screen inlet end, respectively, with the vibration generating means mounted to be horizontally at the center of gravity of the screen basket assembly;

FIGS. 5A, 5B, and 5C are diagramatic views illustrating the orbits of the screen at the screen discharge end, center of gravity of the screen basket assembly, and screen inlet end, respectively, with the vibration generating means mounted intermediate such center of gravity and the screen discharge'end; and

FIG. 6 is an enlarged, fragmentary sectional view taken on line 66 of FIG. 2, looking the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, FIG. 1 illustrates a vibratory separating apparatus designated generally as 10 which comprises a generally horizontal base 12 mounted on rubber mountings l4carried by piers 16. The usual screen basket assembly I8 is positioned within the base 12 and supported or suspended from the base 12 in a manner to be hereinafter described. The basket assembly 18 comprises a generally horizontal screen 20 which, although illustrated as formed from two elongated, juxtaposed, laterally spaced screen sections 22 having separating openings 24 through their thicknesses, could alternatively comprise only a single screen section 22 or more than two of such seetions 22. The screen sections 22 could, for example, each be constructed from abutting perforated plates.

The basket assembly 18 includes a supporting means I which is illustrated as comprising generally upright or vertical side supporting walls 26, 28 rigidlyaffixed to the remote sides of the screen sections 22, and a third generally upright or vertical supporting wall 30 located intermediate adjacent sides of the screen sections 22 and rigidly affixed thereto. In the event that the screen 20 included only a single screen section 22, the wall 30 would normally be eliminated; in the event that the screen 20 was formed from more than two sections 22, additional walls 30 could be provided intermediate adjacent sides of the sections 22. The basket assembly 18 has a pair of supporting elements 32 which extend across the screen 20 above the screen upper or feed face 34 and which are rigidly affixed to the supporting walls 26, 28 30 by mounting brackets 36, 38, 40, re-

spectively. The ends 32a of the supporting elements 32 overhang the supporing walls 26, 28 and connect the basket assembly 18 to a mounting means which suspends the basket assembly 18 from the base 12 for orbital vibrating movement relative to the base 12.

More particularly, as shown in FIG. 1, this mounting means comprises a resilient mounting element 42, constructed of rubber or rubber-like material, supporting each of the ends 32a of the supporting elements 32. The resilient mounting elements 42 each are rigidly connected at their lower ends to the base 12 and at their upper ends carry mounting brackets 44 directly supporting the ends 32a of the supporting elements 32. The mounting elements 42 are each arranged on a generally vertical axis and are resilient laterally and longitudinally to be longitudinally extensible and compressible during the operation of the apparatus to permit orbital vibrating movement of the basket assembly 18 relative to the base 12.

The apparatus 10 includes inlet means for supplying the material to be separated to the upper screen face 34 at the inlet end of the screen such that the material is generally uniformly distributed across the screen sections 22. This inlet means is illustrated as comprising a supply pipe 46 connected at one end to a pressurized source (not shown) of the pulp slurry or other material to be separated, and an inlet compartment or manifold 48 communicating the other end of the supply pipe 46 over an apron 49 with the upper screen face 34 at the inlet end of the screen 20. The manifold 48 contains the usual distribution baffle 50 and extends across the entire cross-section of the screen 20. It will be understood, however, that this illustrated inlet means has been shown by way of example only and alternatively other suitable arrangements could be employed for supplying the material to the upper screen face 34. The screen 20 is arranged to discharge material rejected by the openings 24 from the upper screen face 34 at the other or discharge end of the screen 20; and a discharge trough 52 or other suitable conventional arrangement may be provided at the discharge end for conveying the discharged rejected material from the apparatus 10. The base 12 contains a reservoir or vat beneath the screen 20 and in communication with the openings 24 to receive accepted material flowing through the latter, such vat also communicating with an accepts discharge conduit 54 which discharges such accepted material from the apparatus 10. The apparatus 10 is also provided with the usual showers for diluting the rejected material on the upper screen face 34 adjacent to the end of the screen 20 at which the rejected material is discharged, such showers each comprising a shower header or manifold 56 and shower discharge pipes 58 communicating with the manifold 56 and suspended therefrom.

The vibration generating means of the apparatus 10 comprises a rotatable supporting shaft 60 arranged to extend generally transversely to the screen 20 above the latter, and eccentric weight means mounted on the shaft 60 for rotation therewith. More particularly, as shown in FIG. 3, adjacent to each of its ends the shaft 60 is provided with a reduced diameter portion 62 having a key 64. The reduced diameter portions 62 each carry a cover 66 having an integral eccentric weight 68 keyed to the key 64 for rotation with the shaft 60 and inwardly of the cover 66 a second eccentric weight 70 also keyed to the key 64 for rotation with the shaft 60.

The eccentric weights 68, are all offset to the same side of the longitudinal axis of the shaft 60 and are maintained so offset throughout the operation of the apparatus 10. The shaft 60 is rotatably driven by a drive motor, shown in broken lines in FIG. 1 as 72 and preferably electrically powered, through a conventional flexible drive coupling designated generally as 74 in FIG. 1.

The vibration generating means is mounted on ledges 26a, 28a of the supporting walls 26, 28 of the basket assembly 18 by a mounting means particularly constructed and arranged for so mounting the vibration generating means at a plurality of alternative positions adjusted longitudinally of the screen 20 whereby the rate of advance of material longitudinally along the upper screen face 34 is adjustable independently of the intensity and the amplitude of the produced vibrations by varying the location at which the vibration generating means is mounted on the ledges 26a, 28a by the mounting means.

More specifically, as illustrated, this mounting means comprises a pair of bearing housings 76, each surrounding one end of the shaft 60 and containing bearings (not shown) rotatably supporting their respective end of the shaft 60. The bearing housings 76 are formed integrally with an intermediate tubular element or sleeve 78a which surrounds the shaft 60 intermediate the bearing housings 76. Each of the bearing housings 76 includes integral feet 78 projecting from its opposite sides; and the feet 78, as best shown in FIG. 2 contain slot-like mounting openings 82 which are elongated in the longitudinal direction of the screen 20. The bearing housings 76 are each located on a mounting plate 79 supported on the ledge 26a, 28a of one of the side walls 26, 28; and the bearing housings 76 are mounted to the ledges 26a, 280 by mounting bolts 80 which extend through the mounting openings 82, aligned mounting openings 77 in the mounting plate 79 and mounting openings 84 formed in the ledges 26a, 28a adjacent the center of gravity of the basket assembly 18. (In the illustrated embodiment of the invention, the center of gravity of the basket assembly 18 is at the longitudinal midpoint of the screen 20 and in most embodiments of the invention such center of gravity and longitudinal center will coincide.) The mounting bolts 80, as shown in FIG. 6, are each provided with a nut 81, a relatively thick washer 86 and a lock washer 88.

The mounting openings 82 in the bearing housing feet 78 are constructed sufficiently larger than the corresponding mounting openings 77, 84 to permit housings 76 to be affixed on the side wall ledges 26a, 28a in a plurality of alternative positions adjusted longitudinally of the screen 20. One of these alternative positions is particularly selected such that the bearing housings 76 locate the supporting shaft 60 and its carried eccentrics to be horizontally at the center of gravity of the basket assembly 18 (i.e.,' at the center of gravity in the direction longitudinally of the screen 20). Another of these alternative positions is such that the bearing housings '76 locate the supporting shaft 60 and eccentrics at a position spaced from said center of gravity, but adjacent thereto on the side of the center of gravity towards the end of the screen 20 from which rejected material is discharged. In FIG. 1, the shaft 60 and bearing housings 76 are shown in broken lines as mounted horizontally at the center of gravity of the basket assembly 18 and in solid lines are depicted as mounted intermediate such center of gravity and the end of the screen 20 from which the rejected material is discharged. The bearing housings 76 are locked in their alternative positions by locking pins 90 received in aligned openings 92, 94 in the bearing housing feet 78 and mounting plates 79, respectively.

A selected alternative position of the bearing housing 76 which is chosen will be determined by the nature of the material being processed by the user of the apparatus 10, as well as by the desired degree of material separation. Accordingly, locking pin openings 92 and 94 are formed, independently, for any one or more alternative positions. That is, a selected position is chosen, the bolts 80 and nuts 81 are torqued to secure the housings 76 thereat, and then openings 92 and 94 are formed and pins 90 are inserted to lock the housings 76 in the just-selected position. Therefore, FIGS. 2 and 6 depict the use of the locking pins 90, with openings 92 and 94 formed therefor, in only one of an infinite number of possible positionings provided along the length of the slot-like openings 82.

In the operation of the apparatus 10, the shaft 60 and carried eccentric weights 68, 70 are rotatably driven by the drive motor 72 such that the rotating eccentrics 68, 70 cause orbital vibrating movement of the basket assembly 18 relative to the base 12. The material to be separated, normally a slurry such as the pulp slurries employed in the manufacture of paper, is supplied to the feed face 34 of the screen 20 at the inlet end of the screen 20 through the supply pipe 46 and the manifold 48. The material, thus supplied to the inlet end of the screen 20, is' moved longitudinally along the feed face 34 (as depicted by the arrows in FIGS. 1 and 2) by the orbital vibrating movement imparted to the basket assembly 18 by the rotating eccentrics 68, 70. During this movement of the material along the screen feed face 34, a portion of the material is accepted by the openings 24 and passes downwardly therethrough to the vat below the screen 20 from whence it is discharged by the conduit 54. The portion of the material completely rejected by the openings 20 is discharged from the feed face 34 of the screen 20 at the discharge end thereof and is transported from the apparatus by the discharge trough 52.

During the aforedescribed operationof the apparatus 10, with the shaft 60 mounted horizontally at the center of gravity of the basket assembly 18, the rotation of the supporting shaft 60 and eccentrics 68, 70 vibrates the screen discharge end, the screen at the center of gravity of the basket assembly 18, and the screen inlet end, respectively, through the orbits depicted diagramatically in FIGS. 4A, 4B, and 4C. The major axes of these orbits are, respectively, the illustrated angles a1, a2, and a3 from the Vertical V. The lengths of the orbits measured along their major axes are L,, L,, and L,, respectively; and the widths of the orbits measured at 90 to their major axes are W W,, and W respectively. The rejected material on the screen feed face 34 is moved longitudinally therealong at a rate commenserate with these angles; and this rate of movement of the rejected material is believed to be advantageous for applications of the apparatus 10 with certain types of material.

During the operation of the apparatus 10, with the shaft 60 mounted intermediate the center of gravity of the basket assembly 18 and the discharge end of the screen 20, the orbits of the screen discharge end, screen at the center of gravity of thebasket assembly l8, and the screen inlet end are, respectively, as shown in FIGS. 5A, 5B, and 5C. The major axes of these orbits are, respectively, the illustrated angles a4, a5, and a6 from the Vertical V. The lengths of these orbits measured along their major axes are a4, a5, and a6, respectively; and the widths of the orbits measured at to their major axes are W W and W respectively.

It will be noted from a comparison of FIGS. 4A and 5A that the 114 shown in FIG. 5A is considerably smaller than the corresponding 011 shown in FIG. 4A Also the width W, of the orbit depicted in FIG. 5A is considerably greater than the width W of the orbit of FIG. 4A, although the lengths L L are identical. Hence, due to the smaller angle a4 and the increased wideness or roundness of the width W of the corresponding orbit, the orbital movement of the screen 20 with the shaft 60 intermediate the center of gravity of the basket assembly 18 and the screen discharge end increases the rate of advance of material longitudinally along the screen feed face 34 over that provided with the shaft 60 horizontally at said center of gravity.

From a comparison of FIGS. 48 and 58, it will be seen that at the longitudinal center of gravity of the basket 18 the angles a2, 015 of the orbits are maintained round and substantially identical. The widths W, and W are substantially the same; and the lengths L, and L are also substantially identical. These orbits at the center of gravity provide good propulsion of material along the screen feed face 34.

As regards the inlet end of the screen 20, a comparison of FIGS. 4C and 5C discloses that angle a6 is tipped forwardly from the Vertical V a significantly larger amount than angle 013. The width W is slightly less than the width W and the length L is substantially the same as L The aforementioned forward tipping of the orbit of a6 contributes to an increase in the rate of material proportion along the screen feed face 34 in the direction of the screen discharge end.

Thus, in certain applications of the apparatus 10 in which the material on the screen feed face 34 would otherwise move undesirably slow (or even possibly stall) adjacent to the screen discharge end, the mounting of the shaft 60 at a location intermediate said center of gravity and the screen discharge end will substantially minimize or eliminate the tendency towards slow movement and/or stalling. Moreover, this increase in the rate of movement of material along the screen feed face 34 is accomplished without variation in the amplitude or intensity of the vibrations.

From the aforegoing, it will be seen that the present invention provides new and improved means for aceomplishing all of the aforementioned objects and advantages. More specifically, it will be seen that such new and improved means in a relatively simple and efficient manner permits adjustment of the rate of material movement longitudinally along the screen feed face 34 without variation in the intensity or. the amplitude of the vibrations. Prior art machines with which I am familiar, to the contrary, have been unable to attain this result due to their inherent inability to vary the configuration of the aforedescribed orbits. For example, those prior art machines in which the screen baskets are mounted on stiff restraining springs are inherently so able as the springs force the screen basket to move in a path substantially perpendicular to the axes of the springs and the lengthwise rigidity of the springs requires the screen basket to move in only a fixed orbital path. Hence, these prior art machines have been unable to permit variance of the rate of material advancement along the screen feed face without corresponding variation in the intensity and/or the amplitude of the vibrations.

It will be understood that, although only a single embodiment of the invention has been illustrated and hereinbefore specifically described, the invention is not limited to merely this single embodiment but rather contemplates other embodiments and variations employing the disclosed concepts and teachings.

I claim:

1. In a vibratory separating apparatus, a base, an assembly including supporting means and a screen connected to said supporting means, said screen having openings for separating material passed longitudinally along one face of the screen into a portion accepted by said openings and a portion rejected by said openings, mounting means mounting said assembly on said base for orbital vibrating movement relative to said base, said assembly mounting means including elastomeric means, extending vertically relative to said one face, fixed to said base at only one end thereof, said assembly being carried by said elastomeric means only by the other end of said latter means, said elastomeric means being unrestrained and unsupported intermediate said one and other ends thereof and comprising a sole coupling of said assembly to said base, said elastomeric means being resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of said assembly relative to said base, vibration generating means including eccentric means adapted to be rotatably driven for causing vibrating movements of said assembly, which movements describe orbits of fixed amplitude or length and of given widths and angular inclinations and mounting means for selectively mounting said vibration generating means on said supporting means at an infinite number of alternative positions along a portion of the length of said screen for selectively varying only said widths and angular inclinations of said orbits whereby the rate of advance of material longitudinally along said one face of the-screen is variable independently of the intensity and the amplitude of the vibrations through variation of said widths and angular inclinations by varying the position at which said vibration generating means is mounted on said supporting means.

2. A vibratory screening apparatus according to claim 1, further comprising means for locking said vibration'generating means in at least one of said alternative positions.

3. A vibratory separating apparatus according to claim 1, wherein said mounting means for said vibration generating means comprises bearing housing means containing bearings rotatably supporting said vibration generating means, said bearing housing means and said supporting means having aligned openings therein, retaining means in each aligned set of said openings connect said bearing housing means to said supporting means, and at least one opening of each aligned set thereof is substantially elongated longitudinally of said screen to permit said mounting of said vibration generating means at said infinite number of alternative positions.

4. A vibratory separating apparatus according to claim 3, further comprising means for locking said vibration generating means in at least one of said altemative positions, said locking means including other aligned openings in said bearing housing means and supporting means, and a locking element in each aligned set of said other openings.

5. In a vibratory separating apparatus, a base, a screen basket assembly comprising a screen and supporting walls connected to opposite sides of said screen, said screen basket assembly having a plurality of supporting elements extending across said screen and connected to said supporting walls, said screen having an upper feed face and including openings for separating material passed along said screen feed face into a portion accepted by said openings and a portion rejected by said openings, means for supplying material to be separated to said screen feed face at one end of said screen, said screen discharging said rejected portion from said screen feed face at the other end of said screen, mounting means suspending said screen basket assembly from said base for orbital vibrating movement relative to said base, said assembly mounting means including elastomeric mounting elements extending vertically relative to said feed face, fixed to said base at only one end thereof, said assembly being carried by said mounting elements only by the other ends of said mounting elements, said mounting elements being unrestrained and unsupported intermediate said one and other ends thereof and comprising a sole coupling of said assembly to said base, said mounting elements each being resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of said screen basket assembly relative to said base, vibration generating means for causing vibrating movements of said screen basket assembly, which movements describe orbits of fixed amplitude or length and of given widths and angular inclinations, said vibration generating means including a shaft extending transversely of said screen and eccentric means carried by said shaft, mounting means for selectively mounting said vibration generating means on said supporting walls at an infinite number of alternative positions along a predetermined portion of the length of said screen for selectively varying only said widths and angular inclinations of said orbits whereby the rate of advance of material longitudinally along said screen feed face is variable independently of the intensity and the amplitude of the vibrations through variation of said widths and angular inclinations by varying the position at which said vibration generating means is mounted on said supporting walls by the mounting means, one of said alternative positions being horizontally at the center of gravity of said screen basket assembly and another thereof being adjacent said center of gravity on the side thereof towards said end of said screen at which rejected material is discharged from the upper face thereof, and locking means for locking said vibration generating means in at least one of said alternative positions, said mounting means for said vibration generating means including a bearing housing adjacent each of said supporting walls, said bearing housings containing bearings rotatably supporting said shaft and having flanges projecting from their opposite sides, said flanges and said supporting walls having aligned openings therein, and retaining means in each aligned set of said openings connecting said bearing housings to said supporting walls, at least one opening of each aligned set thereof being substantially elongated longitudinally of said screen to permit material.

8. A vibratory separating apparatus, according to claim 5, wherein said eccentric means comprises a plurality of eccentrics offset to the same side of the axis of said shaft, said screen includes a plurality of juxtaposed laterally spaced screen sections, said screen basket assembly includes an intermediate supporting wall l0- cated intermediate adjacent sides of said screen sec tions, said supporting elements are mounted on said intermediate supporting wall, and said resilient mounting elements each are constructed of rubber-like material.

9. A vibratory separating apparatus, according to claim 5, wherein said locking means comprises aligned locking pin openings in said flanges and supporting walls, and a locking pin in each aligned set of said locking pin openings. 

1. In a vibratory separating apparatus, a base, an assembly including supporting means and a screen connected to said supporting means, said screen having openings for separating material passed longitudinally along one face of the screen into a portion accepted by said openings and a portion rejected by said openings, mounting means mounting said assembly on said base for orbital vibrating movement relative to said base, said assembly mounting means including elastomeric means, extending vertically relative to said one face, fixed to said base at only one end thereof, said assembly being carried by said elastomeric means only by the other end of said latter means, said elastomeric means being unrestrained and uNsupported intermediate said one and other ends thereof and comprising a sole coupling of said assembly to said base, said elastomeric means being resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of said assembly relative to said base, vibration generating means including eccentric means adapted to be rotatably driven for causing vibrating movements of said assembly, which movements describe orbits of fixed amplitude or length and of given widths and angular inclinations and mounting means for selectively mounting said vibration generating means on said supporting means at an infinite number of alternative positions along a portion of the length of said screen for selectively varying only said widths and angular inclinations of said orbits whereby the rate of advance of material longitudinally along said one face of the screen is variable independently of the intensity and the amplitude of the vibrations through variation of said widths and angular inclinations by varying the position at which said vibration generating means is mounted on said supporting means.
 2. A vibratory screening apparatus according to claim 1, further comprising means for locking said vibration generating means in at least one of said alternative positions.
 3. A vibratory separating apparatus according to claim 1, wherein said mounting means for said vibration generating means comprises bearing housing means containing bearings rotatably supporting said vibration generating means, said bearing housing means and said supporting means having aligned openings therein, retaining means in each aligned set of said openings connect said bearing housing means to said supporting means, and at least one opening of each aligned set thereof is substantially elongated longitudinally of said screen to permit said mounting of said vibration generating means at said infinite number of alternative positions.
 4. A vibratory separating apparatus according to claim 3, further comprising means for locking said vibration generating means in at least one of said alternative positions, said locking means including other aligned openings in said bearing housing means and supporting means, and a locking element in each aligned set of said other openings.
 5. In a vibratory separating apparatus, a base, a screen basket assembly comprising a screen and supporting walls connected to opposite sides of said screen, said screen basket assembly having a plurality of supporting elements extending across said screen and connected to said supporting walls, said screen having an upper feed face and including openings for separating material passed along said screen feed face into a portion accepted by said openings and a portion rejected by said openings, means for supplying material to be separated to said screen feed face at one end of said screen, said screen discharging said rejected portion from said screen feed face at the other end of said screen, mounting means suspending said screen basket assembly from said base for orbital vibrating movement relative to said base, said assembly mounting means including elastomeric mounting elements extending vertically relative to said feed face, fixed to said base at only one end thereof, said assembly being carried by said mounting elements only by the other ends of said mounting elements, said mounting elements being unrestrained and unsupported intermediate said one and other ends thereof and comprising a sole coupling of said assembly to said base, said mounting elements each being resilient laterally and longitudinally to be longitudinally extensible and compressible to permit orbital vibrating movement of said screen basket assembly relative to said base, vibration generating means for causing vibrating movements of said screen basket assembly, which movements describe orbits of fixed amplitude or length and of given widths and angular inclinations, said vibration generating means including a shaft extending transversely of said screen and eccentric means carried by said shaft, mounting means for selectively mounting said vibration generating means on said supporting walls at an infinite number of alternative positions along a predetermined portion of the length of said screen for selectively varying only said widths and angular inclinations of said orbits whereby the rate of advance of material longitudinally along said screen feed face is variable independently of the intensity and the amplitude of the vibrations through variation of said widths and angular inclinations by varying the position at which said vibration generating means is mounted on said supporting walls by the mounting means, one of said alternative positions being horizontally at the center of gravity of said screen basket assembly and another thereof being adjacent said center of gravity on the side thereof towards said end of said screen at which rejected material is discharged from the upper face thereof, and locking means for locking said vibration generating means in at least one of said alternative positions, said mounting means for said vibration generating means including a bearing housing adjacent each of said supporting walls, said bearing housings containing bearings rotatably supporting said shaft and having flanges projecting from their opposite sides, said flanges and said supporting walls having aligned openings therein, and retaining means in each aligned set of said openings connecting said bearing housings to said supporting walls, at least one opening of each aligned set thereof being substantially elongated longitudinally of said screen to permit said mounting of said vibration generating means at said infinite number of alternative positions.
 6. A vibratory separating apparatus according to claim 5, wherein said screen includes a plurality of juxtaposed laterally spaced screen sections, said screen basket assembly includes an intermediate supporting wall located intermediate adjacent sides of said screen sections, and said supporting elements are also mounted on said intermediate supporting wall.
 7. A vibratory separating apparatus, according to claim 5, wherein said resilient mounting elements each are generally vertical and constructed of rubber-like material.
 8. A vibratory separating apparatus, according to claim 5, wherein said eccentric means comprises a plurality of eccentrics offset to the same side of the axis of said shaft, said screen includes a plurality of juxtaposed laterally spaced screen sections, said screen basket assembly includes an intermediate supporting wall located intermediate adjacent sides of said screen sections, said supporting elements are mounted on said intermediate supporting wall, and said resilient mounting elements each are constructed of rubber-like material.
 9. A vibratory separating apparatus, according to claim 5, wherein said locking means comprises aligned locking pin openings in said flanges and supporting walls, and a locking pin in each aligned set of said locking pin openings. 